(Meth)acrylic acid is generally prepared by gas phase oxidation of propane, propylene, (meth)acrolein, and the like in the presence of a catalyst. For example, propane, propylene, and the like are converted to (meth)acrylic acid through (meth)acrolein by gas phase oxidation in the presence of an appropriate catalyst in a reactor, and a reaction product mixed gas including (meth)acrylic acid, non-reacted propane or propylene, (meth)acrolein, an inert gas, carbon dioxide, water vapor, and various organic by-products (acetic acid, heavies, and the like) is obtained in the back end of the reactor.
The (meth)acrylic acid-containing mixed gas contacts an absorption solvent such as process water in a (meth)acrylic acid absorption tower, and is recovered as a (meth)acrylic acid aqueous solution. Further, (meth)acrylic acid-stripped insoluble gas is recycled for a synthesis reaction of (meth)acrylic acid, and a part thereof is incinerated and discharged. The (meth)acrylic acid aqueous solution is distilled and purified to obtain (meth)acrylic acid.
Meanwhile, various methods of controlling process conditions or a process sequence and the like to improve the recovery efficiency of (meth)acrylic acid have been suggested. Representatively, as a method for separating water and acetic acid from the (meth)acrylic acid aqueous solution obtained in the (meth)acrylic acid absorption tower, an azeotropic distillation method using a hydrophobic solvent in a distillation column is known. The azeotropic distillation method is a method of effectively recovering (meth)acrylic acid by recovering acetic acid, which is a main by-product of (meth)acrylic acid synthesis, together with water, through a distillation process using a hydrophobic solvent.
Particularly, the inventors have suggested in Korean Laid-Open Patent Publication No. 2009-0041355 that a hydrophobic solvent is used in a distillation column, and acetic acid containing waste water recovered from the upper part of a distillation column is recycled to a (meth)acrylic acid absorption tower and reused. As such, the azeotropic distillation method in a distillation column has the effects of reducing the amount of waste water, and simultaneously, effectively inhibiting inflow of organic substances, and simplifying the subsequent purification step.
However, the azeotropic distillation method and previously disclosed recovery methods of (meth)acrylic acid have problems in that a large amount of energy is consumed in the process of distilling a (meth)acrylic acid aqueous solution, treatment load in the distillation process is high, and a polymer is produced due to polymerization of (meth)acrylic acid to render normal operation impossible, thus lowering stability of a process operation.